# How can I search molecules by constituent atoms

Given a set of atoms, I would like to find (some / the most common) molecules that include only (some/all) atoms of the set. Is there any online search engine that can do this?

E.g. Atoms={C,H} --> Molecules={CH$_4$, C$_2$H$_6$, ...}

Note:

• I am looking for known molecules.
• It is OK if I can only find chemical formulae, so without all possible configurations.
• Personally, I doubt so because there are literally millions, if not billions, of compounds that contain C and H (or any combination of atoms that you specify, unless it's something esoteric like Zr, N, Se). Feb 10, 2016 at 22:20
• Is there some database where you could enter a formula like $C_aH_bO_c$ and get molecules ( compounds) that fit (where a,b and c are given integers)? Certainly by the time that you get to 100 carbons there are more unknown possible compounds than known ones.
– MaxW
Feb 10, 2016 at 22:38
• Pft, you can even check Wikipedia for compounds containing specific elements. Feb 10, 2016 at 23:17
• You can search ChemSpider using a formula for one... chemspider.com/…
– MaxW
Feb 11, 2016 at 3:23
• I'm pretty certain the question here is about searching known molecules, not theoretical ones. There are millions of connected chemical-like graphs with formula N3O4P5 yet I doubt very much that many of them correspond to stable chemical structures! Feb 11, 2016 at 10:02